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Abstract

This thesis attempts to provide end to end encryption within the fixed infrastructure of Home PubHc Land Mobile Network (Home PLMN) and link by link encryption within the GSM PLMN. A new proposal for an authentication protocol for inter PLMN identity and technique for key distribution, achieves end to end encryption and link by hnk encryption across the GSM network. As a consequence of this, the GSM mobile phone user's voice can be completely protected from one point of communication to the other communication point. The receiving end may be within the same home mobile network or may be in a different network but within the GSM service area. We also propose a formal authentication protocol to set up inter PLMN calls, which solves the Border problem, as without the permission or awareness of the Home PLMN, no one can send any encrypted message. However it does provide complete encryption between different mobile networks within the GSM service area. Our proposal attempts to secure the location update between two Visitor Location Register (VLR) locations of a Home PLMN and also to secure international location update between inter PLMN of GSM PLMN, by encrypting important subscriber data being transferred between them.